The battlefield over your house’s thermostat setting has existed for as long as central heating. While some people are too hot, others are shivering miserably in the corner; but what are the reasons for this?
Put simply, our bodies are big watery bags of chemical reactions. Millions of these reactions occur within our cells and, like the household appliances we use every day, they produce a lot of heat as ‘waste’ energy. However, unlike our piping-hot vacuum cleaner after a spring clean, we actually use this heat for our benefit – to maintain a constant body temperature of around 37°C. A change in the amount of heat we make or the heat we retain can cause us to feel colder or warmer than the people around us. How much muscle and fat you have can have a dramatic effect on how much you feel the cold.
Essentially every part of our body continuously generates heat – a process called ‘thermogenesis’. Muscle cells are particularly good at this, producing lots of heat by contracting rapidly (shivering). A recent study also showed that muscles can generate heat without having to shiver, since shivering over long periods can cause damage.
Fat doesn’t produce much heat, but is a very good insulator, helping to ‘trap’ heat in your body, similar to how a coat works. Just think of those chubby little seals that have fat deposits adapted to life in the freezing arctic.
Having lots of fat also tends to make you bigger and decreases your so-called ‘surface area to volume ratio’. Heat escapes from our skin, which can be described as the ‘surface area’ of our bodies; all the other “stuff” in our bodies – muscles, fat, and yesterday’s dinner – makes up the ‘volume’ of our bodies. Small people and babies have a high ‘surface area to volume ratio’, meaning they are more susceptible to the cold because they have relatively more skin for their size.
It doesn’t stop there though. Differences can also be evolutionary, says Dr. Ryan Williams, curator and chair of the department of Anthropology at Chicago’s Field Museum: “in the colder environments, people tend to have shorter, stockier frames to preserve the core temperature in their bodies.”
It’s not just size that matters, either. How warm you feel can also be affected by diet, gender, and metabolic disorders such as hyperthyroidism. Research headed by Professor Dame Nancy Rothwell, President of the University of Manchester, even showed in rat studies that the ability to generate heat appears to decrease with age – so remember to set aside a blanket for your nan.
Therefore, people with plenty of muscle and fat, who eat well, are young and have an active lifestyle will tend to feel the cold less. Conversely, skinny folk who never move from the sofa will always be wanting to turn the heating up. I imagine shot-putters save a fortune on energy bills.
By Michael McKenna
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